Measurement of iron concentration in serum and plasma has been utilized for the diagnosis of anemia, hypoferric anemia, hepatic cirrhosis and the like, and is one of important measurement items in the field of clinical laboratory test.
As the method for measuring iron concentration, for example, colorimetric analysis using various metal chelate color formers such as dipyridyl, o-phenanthroline has been employed commonly, and iron chelate color formers such as sodium bathophenanthroline sulfonate, 2-nitroso-5-(N-propyl-N-sulfopropylamino)-phenol (nitroso PSAP), 3-(2-pyridyl)-5,6-bis[2-(5-furylsulfonic acid)]1,2,4-triazine disodium salt, tripyridyltriazine, ferrozine have been used as a color former.
Since all of these iron chelate color formers develop a color by forming a chelate with divalent iron, on the occasion of using, these require to be used in combination with a reducing agent for the reduction of trivalent iron. As the reducing agent of trivalent iron, L-ascorbic acid, thioglycolic acid, hydroxylamine hydrochloride, hydroquinone, hydrosulfite, sodium sulfite, hydrazine sulfate, metabisulfite (pyrosulfite) and the like have been known.
However, since these reducing agents degrade during storage, the reagents for measuring iron concentration which have been used conventionally had a problem in storage stability of the reagent.
And so, the present inventors have developed a compound represented by the following formula [A] (9-(2-carboxyphenyl)-2,3,7-trihydroxy-6-fluorone, hereinafter abbreviated as CPF) as a dye which reacts with both the trivalent iron and divalent iron (Non-Patent Literature 1).
